This project is concerned with age-related changes in the ciliated protozoan, Tetrahymena thermophila. It is concerned with the accumulation of micronuclear defects with age, and the large differences in rates of accumulation in different lines. It is concerned with particular genes which accelerate some age connected processes. It seeks the mechanisms which distribute life cycle events in time, particularly sexual maturity and allelic assortment. At the theoretical level the project is concerned with mechanisms which yield age related effects by intrinsic cellular programming as opposed to those which act through altered cellular environments.